Conditional same-different categorisation in the short-

beaked echidna

Darren Burke

Fiona Russell

CISAB

Why Echidnas?• Phylogeny

– Monotremes –separate evolutionary path from all other mammals for 120-200 million years

– Mixture of reptilian and mammalian features, considered ‘primitive’

• Interesting Neurophysiology– Large relative brain size– Very large cortex for body size– Unusual cortical organisation– Unusual sensory systems: Electro-receptors

• Adaptable and successful– Doing something right!

Why categorisation?• Interested in having some measure of their

ability to perform a relatively complex cognitive task

• Needed something that didn’t rely on social sensitivity or high visual acuity – or even sophisticated high-level visual categorisation

• Knew echidnas could do visual discriminations (Buchmann & Rhodes, 1978; Gates, 1978)

• Chose conditional same/different categorisation as a measure of their ability to acquire an “abstract” “concept”

General methods• Two choice y-maze• Food dishes covered to prevent use of

olfactory cues (piloted this previously)• stimuli varied to prevent use of low-level

perceptual cues • side of correct stimulus determined by

Gellerman schedule• Rewarded every correct choice• Removed from apparatus between trials

General methods• Two choice y-maze• Food dishes covered to prevent use of

olfactory cues (piloted this previously)• stimuli varied to prevent use of low-level

perceptual cues • side of correct stimulus determined by

Gellerman schedule• Rewarded every correct choice• Removed from apparatus between trials

Exp 1: Basic discrimination

• Provide easy trials to teach basic discrimination

• used correction trials

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Number of correct trials/10

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Before board After board

Exp 2: shape discrimination

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Exp3: Conditional shape discrimination

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Number of correct trials

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S- S+End of correction trials

Exp 4: Same/different categorisation

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Number of correct trials

Transfer stimuli

Training stimuli

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- Transfer stimuli interspersed with training stimuli in test phase (20%)

Exp 5c: conditional same-different discrimination

• Testing for quite complex categorisation

• combining two previously demonstrated abilities – same/different categorisation – conditional discrimination

• First attempt was unsuccessful (Experiment 5a) – Had trouble learning conditionality

• so then separately successfully trained other half of conditional discrimination– different rewarded if black on white

(Experiment 5b)

Training stimuli

Transfer stimuli

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Exp 5c: results

○ = old stimuli

▲ = novel stimuli0

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Number of correct trials

All Stimuli

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Percentage of correct responses

Conclusions• Pitpa successfully performed a conditional same/different

discrimination– A quite complex cognitive feat

• Whether this is a consequence of echidnas possessing a cognitive sophistication to match their neural complexity or of the particular pattern of training she received is a question for future research – With more subjects!